Abandoned mine waste is abundant in most coal mining regions. For example, it was reported that Pennsylvania's Department of Environmental Protection unofficially estimated that between 82 and 140 million cubic yards of coal mining waste material is present in just the forty largest coal mining waste piles in northeastern Pennsylvania's anthracite region alone. See the article titled “Projects to Develop Electricity/F-T Diesel Co-Production Plants Move Forward” published in the March 2001 edition of Hart's Gas-To-Liquids News. Also see the articles titled “His Energy Answer Lies in Coal Industry's Waste” published on Apr. 11, 2001 in the Philadelphia Inquirer and “Coal-to-Oil Plant May Go Up by 2003, Santorum Backs Benefits for Region” published on Nov. 3, 2000 in The Pottsville (Pa.) Republican & Evening Herald. Also see an article published on the Internet and titled “Coal, The Fuel of America's Industrialization, The Fuel of America's Future”.
U.S. Pat. Nos. 6,015,104 and 6,170,770 which issued to John W. Rich, Jr. discloses a process of utilizing coal mining waste to produce a liquid fuel. FIG. 1 of the above referenced patents schematically illustrates a process which includes a reactor vessel 100, known as an entrained flow gasifier, into which oxygen and a carbonaceous slurry is delivered, heated and mixed to generate a synthetic gas, known as raw syngas, and a crushed glass-like aggregate product. The raw syngas is cooled in a cooler 104, scrubbed of fine particulate in a cyclone apparatus 106 and then subjected to a sulfur removing process in apparatus 108. These steps transition the raw syngas into a so-called clean syngas which is input into a slurry phase vessel 110 where the clean syngas is combined with catalysts to yield a wax-like substance referred to as parafin. The parafin is processed to create a range of ultra-clean liquid fuels which are low in particulate, low in aromatics, and substantially free of sulfur and nitrogen, while having a high cetane (ie., energy density) number.
A problem with combining the above referenced gasification and liquefaction technologies is that the synthetic gas delivered into the liquefaction slurry phase vessel must be extremely pure and of a high quality for the liquefaction process to proceed in a superior manner. To this end, any sulfur or hydrogen sulfide present in the synthetic gas will react with the catalyst in the slurry phase vessel and prevent the process from yielding the desired output.
Therefore, there is a need for a method and apparatus which enables the technologies of coal gasification and coal liquefaction to be jointly utilized for generating ultra clean fuels from coal mining waste material. The process and apparatus should include a means of properly conditioning the raw syngas from the gasifier such that it can be effectively utilized to produce ultra clean, sulfur free fuels.